• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3224-3229
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• 2007

This study aims to analyse the influence of steam injection on the performance of hybrid systems combining a solid oxide fuel cell and a gas turbine. The steam is generated by recovering heat from the exhaust gas. Two system configurations, with difference being the operating pressure of the SOFC, are examined and effects of steam injection on performances of the two systems are compared. Two representative gas turbine pressure ratios are simulated and a wide range of both the fuel cell temperature and the turbine inlet temperature is examined. Without steam injection, the pressurized system generally exhibits better system efficiency than the ambient pressure system. Steam injection increases system power capacity for all design cases. However, its effect on system efficiency varies much depending on design conditions. The pressurized system hardly takes advantage of the steam injection in terms of the system efficiency. On the other hand, steam injection contributes to the efficiency improvement of the ambient pressure system in some design conditions. A higher pressure ratio provides a better chance of efficiency increase due to steam injection.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1502-1513
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• 2006

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

• Korean Journal of Breeding Science
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• v.43 no.5
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• pp.349-359
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• 2011

Agriculture plays a vital role in the sustenance of human society and is the fundamental of developing economies. Nitrogen is one of the most critical inputs that define crop productivity. To ensure better value for investment as well as to minimize the adverse impacts of the accumulative nitrogen species in environment, improving nitrogen use efficiency of crop plants is of key importance. Efforts have been made to study the genetic and molecular biological basis as well as the biochemical mechanisms involved in nitrogen uptake, assimilation, translocation and remobilization in crops and model plants. This review gives an overview of metabolic, enzymatic, genetic and biotechnological aspects of nitrogen uptake, assimilation, remobilization and regulation. This review presents the complexity of nitrogen use efficiency and the need for an integrated approach combining physiology, quantitative trait genetics, system biology, soil science, ecophysiology and biotechnological interventions to improve nitrogen use efficiency.

• Journal of IKEEE
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• v.25 no.1
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• pp.133-138
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• 2021

We propose a Ku-band three-stack CMOS power amplifier to enhance the output power and efficiency. To minimize the dc power consumption, the driver stage is designed using common-source structure. To obtain high output power and utilize a voltage combining method, the power stage is designed using stack structure. To verify the proposed power amplifier structure, we design a Ku-band power amplifier using 65-nm RFCMOS process which provide nine metal layers. The P1dB, power-added efficiency, and gain are higher than 20 dBm, 23 dB, and 25%, respectively, while the operating frequency is 14 GHz-16 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.25-32
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• 2021

In this study, it proposes a mode converter that is relatively easy to implement and can shorten the transmission line length of the final combining port and it was fabricated and tested by applying it to an 8-way spatial combiner. The proposed mode converter converts the signal converted from the doorknob-shaped circular disk connected to the ground into the TM₀₁ mode by opening it in the circular waveguide. The 8-way waveguide spatial combiner is designed and implemented so that 8 signals input from the H-plane are combined in a circular waveguide at the center, and the final combining mode is TM₀₁. The test results confirmed excellent performance with an insertion loss of less than 0.4dB and a combining efficiency of 95% or more. In addition, it was confirmed that it is suitable for high output by calculating the breakdown voltage and discharge threshold power of the new mode conversion structure through electric field analysis. The results confirmed through this study are expected to be applicable to high-power, high-efficiency SSPA in various fields in the future.

• Korean Journal of Optics and Photonics
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• v.32 no.1
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• pp.1-8
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• 2021

We have studied a tiled-aperture coherent-beam-combining system based on constructive interference, as a way to overcome the power limitation of a single laser. A 1-watt-level, 3-channel coherent fiber laser and a 3-channel fiber array of triangular tiling with tip-tilt function were developed. A monitoring system, phase controller, and 3-channel phase modulator formed a closed-loop control system, and the SPGD algorithm was applied. Eventually, phase-locking with a rate of 5-67 kHz and peak-intensity efficiency comparable to the ideal case of 53.3% was successfully realized. We were able to develop the essential elements for a tiled-aperture coherent-beam-combining system that had the potential for highest output power without any beam-combining components, and a multichannel coherent-beam-combining system with higher output power and high speed is anticipated in the future.

• Journal of the Korean Data and Information Science Society
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• v.13 no.2
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• pp.55-64
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• 2002

In this paper, we introduce SVM(support vector machine) developed to solve the problem of generalization of neural networks. We also introduce boosting algorithm which is a general method to improve accuracy of some given learning algorithm. We propose a new algorithm combining SVM and boosting to solve classification problem. Through the experiment with real and simulated data sets, we can obtain better performance of the proposed algorithm.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.3
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• pp.25-30
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• 1995

A new finishing process, magnetic-electrolytic-abrasive polishing(MEAP), combining Lorentz' force effect in the traditional electrolytic finishing process was developed to realize the high efficiency as well as high surface quality of finishing . The paper describes the theoretical basis about the modification of electrolytic ions motion by the magnetic field. The effect of magnetic field on the electrolytic process was discussed was and analyzed from the result of model test.

• Korean Management Science Review
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• v.14 no.1
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• pp.77-85
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• 1997

This paper proposes an approach for individual selection in genetic algorithms to improve problem solving efficiency and effectiveness. To investigate the utility of combining simulated annealing with genetic algorithm, two experiment are conducted that compare both the conventional genetic algorithm and suggested approach. Result indicated that suggested approach significantly reduced the required time to find optimal solution in moderate-sized problems under the conditions studied. It is also found that quality of the solutions generated by suggested approach in large- sized problems is greatly improved.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.108-113
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• 1991

In this paper, an improved method for tracking maneuvering target is proposed. The proposed tracking filter is constructed by combining the input estimation approach with the variable dimension filtering approach. In this approach, the filter also provides the estimated time instant at which target starts maneuver, when the target maneuver is detected. Using this estimated maneuvering time, the maneuver input is estimated and the tracking system changes to the maneuver model. Simulations are performed to demonstrate the efficiency of the proposed tracking filter.